spaco wrote:
I use both red and blue layout dye, but you can use a felt tip marker
just as well.
But, if you are using it to test a fit or to test flatness, you need
"High Spot Blue" which is a blue paste that comes in a little tube,
like toothpaste. MSC has that. I have often wondered why one couldn't
just get a tube of prussian blue oil paint, instead.

We use a big chisel-point sharpie for casual layout scribing all the
time in the shop -- it's handier, neater and dries faster than the
layout blue. But the official stuff is tougher, stays visible even as it
gets hot while grinding to the line and so is still used quite often.

And yes, artist's oil Prussian blue is not only usable for high-spot
marking but is often preferred by machinists claiming that some brands
have more pigment.

--
Ron Hock
HOCK TOOLS www.hocktools.com